"The Imitation Game" is a film that traffics in unbreakable codes, cryptic ciphers and impossible puzzles, but beneath its affection for complexity, it's really this simple: Director Morten Tyldum's World War II drama, based on an extraordinary true-life story, is all about Benedict Cumberbatch.

Not that the English actor's on-screen excellence -- or his versatility -- should come as a surprise. Since his lead role in the BBC series "Sherlock" transformed him into a celebrity sensation a few years back, he's turned in memorable performance after memorable performance. That's proven true whether he's playing a mole-hunting spook ("Tinker Tailor Soldier Spy"), an awkward and wounded man-child ("August Osage County") or a benevolent slave owner ("12 Years a Slave").

As if to prove his range, this holiday season alone, in addition to his role as the brilliant but troubled British cryptanalyst at the center of Tyldum's "Imitation Game," Cumberbatch also plays a talking wolf ("Penguins of Madagascar") and a fire-breathing dragon ("The Hobbit: Battle of the Five Armies").

So, yeah, the guy can act.

But even knowing that, it's hard not to stand in awe of his layered turn in "The Imitation Game." It fact, it almost feels as if his career has been leading up to this particular role for some time. That's because in Tyldum's film, he plays a character who is confident and resourceful (as was his character in "Tinker Tailor Soldier Spy"), brilliant but exasperating ("Sherlock"), noble but conflicted ("12 Years a Slave") and vulnerable and tragic ("August, Osage County"). In this case, however, he does it all at once, all in one character, and still with the utmost credibility.

That character is Alan Turing, a gifted English mathematician and cryptanalyst (that's a "codebreaker" to you and me) who is as tragic a figure as he is a historic one -- and who ranks up there with Nikolai Tesla when it comes to overlooked geniuses.

As a father of modern computer science -- some would say the father of modern computer science -- the pioneering Turing was instrumental in the efforts of England's Secret Intelligence Service to crack messages encrypted by Germany's iconic Enigma machine, then considered by most to be unbreakable. And for most people, it was unbreakable. Turing, though, was wired differently than most people.

His novel approach, then considered by many to be crazy -- but by him to be only logical -- was as audacious then as it seems natural now: If human brain power couldn't break the code, why not build a machine to imitate thousands, even hundreds of thousands, of human brains? (I won't tell you how it ends, except to point out that we all still speak English instead of German.)

But as gifted as Turing was, he is an equally tragic figure. Like so many with gifts in one area, he was deficient in others. While he managed to crack one of the world's most notoriously complex codes, there was another code that Tyldum's film tells us he couldn't crack: basic human interaction.

Turing's mother, he says in the film, considered him "an odd duck." The rest of us, tragically, would -- and did -- uncharitably consider him a weirdo.

It has been argued that Turing suffered from Asperger syndrome and that it was the root of his trouble connecting with others. Of course, diagnosing someone decades after his death is a tricky proposition, but Tyldum's film -- as reflected in Cumberbatch's performance, with its myriad tics and twitches -- clearly buys into that argument. And while Graham Moore's screenplay isn't without its flaws, it brilliantly weaves into the story a case that being different shouldn't necessarily be a negative thing. In fact, "The Imitation Game" argues in no uncertain terms that those differences can be something to celebrate, not to "cure."

That message is hammered home in the film's suspenseful third act, which -- despite its tendency to dip a toe into melodramatic waters -- is a powerful and well-conceived one. (I can imagine parents of children with autism spectrum disorders finding a lot to like, and a lot to be inspired by, in "The Imitation Game.")

Texturally, Tyldum's film feels as if it could be a companion piece to "The King's Speech" -- which is to say that it boasts admirable production quality but that it is held back aesthetically by Tyldum's overly conventional approach. The only flourishes that come even close to outside-the-box are in his occasional, and jarring, use of flashbacks from Turing's childhood and flash-forwards to his post-war experiences.

Both periods in Turing's life are key parts of his story, and both help to drive home the film's "god bless the odd ducks" message. But Tyldum's approach to them doesn't always work.

That being said, the assets here -- including a strong supporting cast that includes Keira Knightley and Matthew Goode -- far outweigh the liabilities. Despite its title, Tyldum's film isn't some imitator or wannabe. Rather, "The Imitation Game" is the real deal.

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THE IMITATION GAME 4 stars, out of 5

Snapshot: Benedict Cumberbatch stars in a World War II drama based on the true story of British cryptanalyst Alan Turing, who is credited with cracking Germany's until-then unbreakable Enigma code.

What works: Cumberbatch turns in a top-shelf performance, and woven into the script is a wonderful "embrace the odd ducks" message.

What doesn't: Tyldum's direction is conventional to a fault, and it is further hurt by jarring flashbacks and flashforwards that only interrupt the film's momentum.